valid_shadow - controls which objects can be shadowed

int valid_shadow( object ob );

When  an  object  attempts  to  shadow  'ob'  (with the shadow() efun),
valid_shadow in the master object is called.  One object  parameter  is
passed,  which  is  the  object that previous_object() is attempting to
shadow.  valid_shadow() should return 0 if the  shadow  should  not  be
permitted,  in which case the shadow() call will return 0 and fail.  If
valid_shadow() returns 1, the shadow is allowed.

shadow(3), query_shadowing(3)